


Not So Differential After All

by attackstance



Category: SuperM (Korea Band)
Genre: Alternate Universe - College/University, Cock Slut, Feminization, M/M, Smut
Language: English
Status: Completed
Published: 2020-03-21
Updated: 2020-03-21
Packaged: 2021-02-28 21:33:30
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,254
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23244064
Author URL: https://archiveofourown.org/users/attackstance/pseuds/attackstance
Summary: A tutoring gig and a misplaced diary give Mark Lee's daily schedule an unexpected upgrade.
Relationships: Mark Lee/Wong Yuk Hei | Lucas
Comments: 21
Kudos: 639
Collections: Himbo Hive





	Not So Differential After All

**Author's Note:**

> Written for Himbo Hive k-pop bingo square “Can’t do basic math.” Based on [this](https://i.imgur.com/PG1QcLo.png) tweet.
> 
> Russian translation by [_haepaliii](https://twitter.com/_haepaliii) found [here.](https://ficbook.net/readfic/9209490/23577149)

Other than Tuesdays and Thursdays, Mark Lee is a relatively normal young man with a relatively normal daily schedule.

He has two morning lectures, two afternoon lectures, and a job cashiering in the university bookstore until closing at 8PM—if he’s lucky. He studies between classes, between meals, between naps, since maintaining a modest 4.0 GPA doesn’t leave a lot of room for drunken midnight bar crawls or heated billiards tournaments with the other members of the physics fraternity. Even if he had the time, Mark has a sterling image to uphold, a black-and-white code of morals, a dated sense of honor and chivalry that exasperates his dearest of friends. Diligence is his ally in every battle.

Other than on Tuesdays and Thursdays, Mark Lee is a role model for his fraternity, for the university, for the community. There’s not a single chink in his gleaming armor or smudge on his flawless record, and any student or faculty he’s encountered will tell the same story, word for word.

Then, Tuesdays and Thursdays come.

And Mark Lee becomes a vulgar, perverse, depraved worm of a human being who shouldn’t be allowed to lick the soles of a horse stall cleaner’s boots—in his eyes, that is.

On Tuesdays and Thursdays, Mark has one morning lecture, a few hours of undergraduate research and then, at 2:30PM on the dot, Mark tutors for the physics fraternity—

No, more like Mark tutors a football player for the physics fraternity—

 _No,_ more like Mark tutors Yukhei Wong, oppressively tall offensive tackle for the university’s football team, vice-chair of the student government association, co-organizer of the biggest summer charity run on campus and all-around good guy, for the physics fraternity.

Mark didn’t meet Yukhei Wong until fall semester of their junior year, though he’s heard of him since freshman year. It’s not often in a campus as big as theirs that a single name gets passed around as easily as mono, but Yukhei has always apparently been bigger than his already big body can contain, in personality, achievements, skills, looks. His name reacquainted itself with Mark’s ears each time he forgot it until Mark couldn’t forget it anymore, that mysterious and faceless entity who had all the freshmen and later, the sophomores charmed.

Junior year comes and Mark is assigned a regular tutoring gig after assuring his frat brothers he can handle the extra workload. Their frat doubles as a math tutoring source when the student learning center is booked solid. A perpetually harried young man, Mark skimmed the email before rushing to their meeting in the physics building commons, his impending doom looming just overhead until his tutee shakes Mark’s small hand in his large one, smiles something friendly and introduces himself as Yukhei Wong. Now, Mark has a face to put the name. A face, a deep voice, a set of pillowy lips and a pair of wide eyes, the length of wide shoulders and the swell of biceps underneath a tight t-shirt. It’s all Yukhei, all of it and more, and there Mark is crushed underneath that doom.

…on Tuesdays and Thursdays.

He finds a way to curb himself and his sudden cravings after their third tutoring session—after Yukhei spilled water down his chin and rudely lifted his shirt to wipe it away. Mark had to leave early, fingers shaking around his backpack straps, glasses fogged over from the heat dousing his face. He’s not the steadfast pillar of common decency he pretends to be in the face of temptation, and Yukhei is about six feet of walking, talking temptation. He needs relief, he needs sanctuary, he needs an outlet.

So he buys a diary, simple black covering on the outside, wide-ruled paper on the inside, and after each meeting with Yukhei, he writes. Sometimes he writes more—when Yukhei gave him a crushing one-armed hug after acing a quiz—and sometimes he writes less—when Yukhei is gloomy after a rough home game. The point is, Mark _writes_ as soon as he gets back to his apartment, every raunchy fantasy and lewd urge that plagues his mind during the hour he spends in Yukhei’s presence immortalized in innocent blue ink, and after he finishes, he breathes a tortured sigh, wipes the sweat from his forehead, and continues living his relatively normal young life.

It’s a flawless system, until it isn’t.

Or, more specifically, until Mark fucks up the system by scooping a messy pile of books and notebooks into his backpack while packing up for another Thursday session, then dumping the contents of bag on the table in search of an extra pencil for Yukhei, and _then_ rushing out after getting an email about an all-you-can-eat waffle bar at the dining hall across campus. He’s baffled once he gets home and doesn’t see his precious diary on his nightstand, baffled twofold when he tears his room apart and finds nothing. He never takes it out of his room and his nosy roommate is training abroad in the Galapagos for a week, so there’s no chance of it ending up in the wrong hands.

“This is bad, this is bad bad bad,” Mark chants as he paces the living room, already feeling the restless energy inside him mounting without his usual outlet. He’ll do something crazy if he doesn’t release it soon, something he’ll regret and never be able to look Yukhei in the eye for.

No!

“No!” Mark scolds himself. He’s not a teenager, he won’t let his dick rule his every action anymore. “I’ll just…hold out until I can find it. Yeah, yeah, this is cool. This is fine. No sweat!”

Mark takes a deep breath to calm himself.

Yukhei Wong is confused.

This isn’t the usual brand of confusion he’s gotten use to on Tuesdays and Thursdays, when his math tutor is pelting him with differential calculus rules. He knows how to handle that, either by manually shutting off his brain or by pouting until his tutor caves to pity and helps him solve problems step-by-step.

This confusion is something Yukhei doesn’t figure out how to approach until after three consecutive days of wrestling with it—or, alternatively, three consecutive days of jacking off to it until his dick skin is raw.

The source of this confusion is the diary now in his possession, simple on the outside yet with innards too complex for Yukhei to fully process without regular blood flow to his head. His tutor, the studious everyman Mark Lee he’s heard tell of since freshman year, had left the small notebook behind after running out after the end of their Thursday session with mutters of “Waffle time, waffle time,” under his breath. Yukhei hadn’t been quick enough to call Mark back to return his things, so it left him with a sheet of half-worked math problems, an unlabeled notebook too ordinary to not be suspicious, and a hearty curiosity that controls his hands before his conscience can reprimand them.

Later, he’ll feel guilty and claim his actions were driven by hopes of finding calculus tips in Mark’s possession, but it’s such an obvious lie. After enough semesters of occasionally hearing of the uncannily brilliant and infectiously kind future valedictorian of their year, Yukhei can’t help wanting to see something beyond the surface of the immaculate Mark Lee. Mark gives nothing away during their sessions, stifled snorting laughs when Yukhei makes jokes, vague dismissals when Yukhei asks about his weekend plans, nervous stammers and immediate topic switching when Yukhei even slightly attempts flirting. It’s a polish that Yukhei finds intimidating. Being intimidated is fundamentally at odds with who Yukhei is. He _loves_ people and sees no good reason he and Mark shouldn’t be friends, if only he had a line to grasp.

He expects that line to be mention of a clay turtle shell collection, or a sketch of a mountainous hiking trail, or a shared interest in shoujo-style anime.

He doesn’t expect it to be a series of incredibly carnal diary entries with descriptions more intense than any hardcore porn he’s jacked off to.

Yukhei reads a single line of the first entry after Mark is gone, flushes out to his ears with dark eyebrows hiked high, and quickly shoves his things into his backpack to head home. For privacy.

“Holy…wow,” he breathes once he’s in the safety of his locked bedroom, cracking open the diary the second his ass hits his desk chair.

_September 3rd,_

_Oh man oh man, I was totally not expecting that. I guess it makes sense since you’re an athlete and all, but I wasn’t expecting to just see your body like without warning. I can deal with seeing the arms all the time, but the abs just…fuck, dude. I really wanted to ask if I could touch them right there, hah. No, that’s a lie. I wanted to get down under the table and blow you right then and there while you studied. I wouldn’t care if anybody else heard or saw me as long as I got to please you. Fuck, the things I’d do just to choke on your dick once, I swear I’d be set for life. Would you fuck my throat raw if I asked, too? Until I can’t talk anymore? Until your dick is all I can taste? God, you’re such a big guy too, I think you’d drown me if you shot your load down my throat, but I mean, I gotta go sometime, right? Haha, jokes jokes._

It’s the first of many unsent lewd letters to an unknown recipient, and the first of many sudden boners for Yukhei. He already thought of Mark as kind of cute, with cheekbones out of this world and an ass too perky to be hidden behind dismal tan slacks, but that Mark and _this_ Mark are two different people and Yukhei’s dick agrees as much. The diary entry paints the picture before Yukhei can stop it, Mark dirtying his creased slacks on the floor, eyes glistening as he pulls a faceless stranger’s dick out and sucks like his life depends on it, tear tracks fresh and the corners of his lips raw as that stranger reams his mouth and logs throat with enough cum to spurt out of his nose.

Yukhei’s eyes snap before he realizes they closed and his hand pauses where its unconsciously palming his dick. He should stop now, he _should_ have stopped before he even opened the diary. Mark is a good man and doesn’t deserve to have his privacy invaded after all the help he’s given Yukhei, but Yukhei has already taken the first bite of the apple and now temptation is coiled around his wrists, guiding him to flip the page to the next entry. It’ll be the last one, or so he promises himself. “Just…one more.”

_September 5th,_

_You’re wearing sweats today, like legit you’re actually wearing the football team’s sweats. Are you crazy? When you walked in my heart almost fell out of my ass, I swear. I knew you were big, but I didn’t know you were BIG, you know what I mean? I’m gonna need a couple more fingers to get ready for you, huh? Or wait, maybe I shouldn’t? I kinda want it to hurt when you fuck me so I always remember I’m yours, want you stretch me out around your cock like one of those fleshlights things. Look, I know that sounds weird, but honestly I’d love to be your fucktoy. You could fuck me whenever, wherever you want and I’ll take it. You can leave me gaping and leaking spooge by the big oak tree on the quad and I’d wait for you to come back and use me again. I want everyone to see me too, so I can proudly tell them I’m your fleshlight. I did gymnastics a while back too so I’m really flexible! Not a lot of people know that. You can fold me any way you want and I won’t break! …unless you want me to?_

The more Yukhei reads, the more he wishes he had a face to put to the champion of Mark’s fantasies. To convert pristine Mark Lee into a part-time erotica author, the man in question must be a total knockout. The only lead Yukhei has is that it’s someone on the football team, but big and athletic doesn’t narrow down his options—and, if Yukhei is being a little less than humble, if Mark is going to crush on a handsome someone on the team, Yukhei should be first in the running.

He convinces himself to read just one more page to find out the man’s identity. “One more isn’t that bad. I’m giving it back, anyway,” he assures himself with a nod.

_September 10th,_

_Aw, man. It’s really dumb, but I got a little jealous when you chatted up this hot girl who walked by our table. I mean, I already kind of guessed you were straight or whatever, but I don’t know. Still…I wonder if you’d ever experiment any? Or if you’d ever just take any hole when you’re horny? Seriously, you don’t have to look at me, talk to me, touch me like that while you’re fucking me. I’ll be your girl if that’s what you want, let you fill my pussy up with your big dick, let you call my dick a clit. Think about it! You can give me a girl’s name, or hell, just call me your slut. I’m already that now, aren’t I? The only thing I’d be sore about is if you didn’t cum in me. You don’t know how much I want you to breed my cunt, knock me up, make me your girl forever—Mrs. Wong. Fuck wait, I’m getting kind of hard writing this. Or should I say wet? Haha…God, I’m so dumb._

It’s no exaggeration to say Yukhei is stupefied for ten minutes straight, eyes nearly tumbling out of their sockets as he stares at the words _Mrs. Wong_ , then he flips through the pages, notes all the dates on them and checks his calendar, realizing each entry was written on a Tuesday or Thursday. He skims the most recent entry and isn’t surprised to remember the details Mark writes, everything down to the flavor of Gatorade Yukhei was drinking that day.

There’s no mistaking it: Yukhei is the lauded champion of Mark’s fantasies.

“Yes!” Yukhei cheers with a vigorous fist-pump. Mark wanting to fuck him just confirmed Yukhei as the hottest guy on the football team. “Fucking knew it.”

His smug grin doesn’t last long. The situation is even more confusing knowing he’s starring as Mark’s charming hump interest and, considering the aggressive throbbing of his boner, Yukhei might be a little interested in the casting offer.

In fact, as he shoves down his pants, grabs his aching dick and continues reading where he left off, he might be a little too interested.

Mark Lee’s Tuesday turns out better than expected.

This isn’t saying much after he’s already woken up late for his morning lecture, accidentally deleted all the data for his lab work, and spilled half his lunch on his nice crisp polo shirt, but Mark is an optimist even when life seems intent on pummeling him to the ground.

Although his diary has yet to be found, Mark is confident in his ability to keep his needs in check for a few days until he can buy a new diary. His plan is to keep the tutoring session strictly professional and focus only on calculus, not Yukhei Wong and his radiant smile and long legs and rich laughter and—

“Mark? You listening to me?”

Mark jumps in his seat, startled gaze on Yukhei across the table from him. Right, he’s supposed to be writing problems for Yukhei to work through but already his carefully curated plan is crumbling under the weight of Yukhei’s prevailing attractiveness. Mark is fighting a losing battle.

Luckily, Yukhei has been just as distracted today and doesn’t notice, not making half the idle chatter he usually does and staring more at his lap than he does his notes. It’s an off day for both of them and Mark considers calling it quits early.

“Sorry. What’d you say?” he asks when Yukhei’s stare doesn’t relent.

“Was just wondering how your weekend went,” Yukhei says. He asks it every Tuesday despite how little Mark has to tell him.

Mark shrugs. “Oh, uh, not much. Just…stuff.” He studies, he works, he volunteers, he gives prospective students tours around campus, nothing he thinks would interest someone as lively as Yukhei Wong.

Yukhei doesn’t seem satisfied with the answer but he doesn’t say anything more. The only sound between them is the scribbling of Mark’s pencil and the tapping of Yukhei’s sneaker under the table. The air between them is unusually stifling and Mark alone isn’t the cause. Sure, he and Yukhei were never friends, but it wasn’t as difficult to hold light conversation as it seems now. For once, the seconds tick by too slowly for Mark.

He makes up his mind. “Hey, so, I’m actually a little tired today. Mind if we stop early?”

Yukhei seizes up, mouth opening and closing in attempt to craft sentences. Mark doesn’t wait for him to speak and starts packing up his things. “We can spend a little extra time on Thursday, if that works for you. Just make sure you finish the problems I already—”

When Mark stands, a strong hand locks around his wrist and pulls him back into his seat. “Please. Wait,” Yukhei chokes out, an expression on his face as troubled as it is constipated. “I’ve gotta tell you something. Uh, and give you something back.”

Mark’s brow pinches as Yukhei rummages through his bag to pull out two items. First, the mechanical pencil Mark let him borrow last week, incredibly cheap and not worth the severity of Yukhei’s tone. Second, a small black notebook that looks awfully similar to…

Now, it’s Mark’s turn to seize up, chest pounding like thunder and water rushing through his ears, legs turning into jelly and lungs turning into stone, brain a frenzy of panicked thoughts as his trembling hand slowly reclaims his diary from the person he wanted least to see it. He’s had nightmares less awful than this, he’d sooner spend the rest of his life in a dark forest running from clown-spider hybrids wielding knives than facing this situation. If his legs were any use, he’d already be out the door and hiding deep in his closet to marinate in his own depravity.

“H…how…h-how did…?” Mark’s unfinished question is spoken with wheezing breath. A few words more and he’ll be hyperventilating.

“You, uh, left it. When you left last time,” Yukhei explains with an awkward sweep of fingers through his hair.

Mark doesn’t have any excuse for his own stupidity other than an anticlimactic “Oh.” Then comes the question he dreads most of all. “Have you…I mean, you didn’t…look inside, did you?” He’s practically pleading with Yukhei to lie to him, they both already know Yukhei’s seen the foul contents of Mark’s brain, but it would make everything so much easier if Yukhei lies to him, so much more bearable. They could pretend this whole thing never happened, win Yukhei his passing grade in calculus and never see each other again after this semester.

Underneath his mountain of desperate hopes, Mark already knows Yukhei Wong is too good a man to lie. “Not…the whole thing?” Yukhei offers as consolation, but still winces once it’s out in the air.

Mark isn’t sure where to start, with begging for Yukhei not to report him to the campus police for sexual harassment or with begging Yukhei not to sock him in the face, both rightfully deserved. Either way, he has to apologize, has to find Yukhei a new tutor who has self-control, has to make this up to Yukhei any way possible.

“Look, I’m sorry, okay? I know it was shit of me to do.”

It takes a few seconds for Mark to realize that wasn’t his voice apologizing. He stares incredulously at the guilty expression Yukhei wears. “You’re sorry? _You’re_ sorry? Why would you be sorry? This is all my fault.”

Yukhei gives him a puzzled frown and Mark gives him one right back. “For looking at your stuff like that. Invasion of privacy or something. It wasn’t cool of me. Don’t be mad?” he says as he gives Mark that deadly pout of his.

There isn’t a worse time for Mark’s heart to pulse with affection yet it does, affection for this sweet guileless man who doesn’t deserve to be burdened with Mark’s lust. “ _Please_ don’t apologize. I shouldn’t have even, ehm,” Mark’s cheeks light up on cue, “…talked about you like that. I’m really _really_ sorry and I swear it won’t happen again. Fuck.” He pushes his glasses up to rub his eyes, the ache behind them growing steadily. “Just, give me a few days and I can find you a new tutor. I know a couple—”

“Woah, wait, stop, what?” Yukhei holds up his palm to interrupt mark. “It’s not like that. I don’t care about that. You’re still getting me through this derivative shit.” He pauses to clear his throat. “I actually thought you’d wanna…y’know. After reading all of that? C’mon, man, you can’t leave a guy hanging.”

Yukhei is blushing, the first Mark’s ever seen it from him. Mark is nervous to ask for clarification but Yukhei’s vague request doesn’t give him much to work with. “What do you mean?” A thought comes to his head and he leans forward to whisper, “I can’t help you cheat or anything, if that’s what you mean.”

Yukhei shakes his head. “No! Just, I thought,” he starts, thinks better of saying whatever it is aloud, and stretches his mile-long arm around the table to yank Mark’s chair beside his instead. Mark’s stomach flutters at the show of strength but he keeps his face impressively neutral…until he has Yukhei’s mouth close to his ear, warm breath grazing the shell and deep voice vibrating down to Mark’s core.

“Thought you wanted me to beat up that pussy of yours.”

In an instant, Mark’s glasses fog over completely and he looks at Yukhei in shock, in disbelief. No way Yukhei is saying what Mark thinks he’s saying, no way he isn’t messing with Mark to get him back for the contents of the cursed diary—but it’s unmistakable, the dark and sober eyes locked with his, the massive hand now crushing the meat of his upper thigh, the notably larger bulge at the front of Yukhei’s jeans.

Yukhei isn’t joking.

Yukhei is interested in him.

And Mark is…Mark is…

“ _Ngh_ , fucking… _yes!_ ”

…Mark is stuffed beyond rational belief.

It’s a Tuesday night, Mark Lee has two early lectures tomorrow, he should be getting ready to sleep right now instead of getting pressed into the surface of his rickety desk with all his textbooks and notes thrown to the floor, naked from the waist down with his trembling legs coiled around Yukhei Wong’s waist.

“C’mon.” Yukhei is panting into Mark’s flushed neck, almost inaudible over the festive clap of his heavy balls against Mark’s lube-slickened ass and the creak of Mark’s abused desk. “Thought you…said you…could take this. You gotta be…my girl,” he huffs behind every brutal drive of his hips, Mark’s body jolting up the desk and his blunt nails anchored into Yukhei’s sweat-layered shoulders.

“I can, I-I am, I— _oh, God…!”_

Yukhei is being unfair, it’s their second go and they had to migrate away from the sticky sheets Mark was too exhausted to change. His sweaty back is sticking to the smooth surface of his desk, his throat is like sandpaper from the screaming Yukhei’s name only an hour ago, his hole is swollen and grips weakly around Yukhei’s unreal girth, and his mind is melting to complete mush the longer Yukhei ravages him. He’s only human but Yukhei fucks him harsher than the stamina-infused machine from Mark’s fantasies. Mark spoke a bold game in his diary and Yukhei is intent on making him live up to every sordid pledge.

“So…fucking good,” Yukhei groans as he nibbles up to Mark’s hairline. His hands are bruising under Mark’s thighs, spreading them as far as they’ll go to make room for himself, for the swirls of his hips as he teases Mark’s ignited body. “Wanna taste your pretty little cunt. It’s mine now, isn’t it?” he says and tugs Mark’s earlobe between his teeth. “Let me eat you out, baby. Need my girl to feel good.”

Mark’s stomach flutters in time with his tender rim—he’s _Yukhei’s_ girl!—and he’s drunkenly nodding before Yukhei finishes talking. He shakily reaches up to tangle his fingers in Yukhei’s hair, urging Yukhei’s mouth down against his collarbone. “Bite. Please.”

Yukhei obliges immediately, teeth clenching tight in his flesh until Mark’s eyes shutter. He pulls away before Mark’s had his fill and kisses him instead. “Not too much,” he warns once he’s freed his bottom lip from Mark’s hungry teeth. “Need you alive for Thursday too.”

The promise of more has Mark attentive and gazing furtively into Yukhei’s eyes, seeing the same fiery sincerity there’s always been.

Mark’s thoughts on Tuesdays and Thursdays? Maybe they’ll need some readjusting.

**Author's Note:**

> [@twt](https://twitter.com/reinefleche)


End file.
